MIXTURES FOR HEAVY GRAY IRON CASTINGS. 279
that the iron was fully the equal of ' air furnace gun iron,' they were satisfied. The great strength and value of Muirkirk pig iron is not a question of a few years, but has been known since the building of the furnace in 1841, or over fifty years. Muirkirk was used during the Civil War for shot, shell, and cannon. It was used in the manufacture of the last cast gun iron mortars made for the United States War Department, and was used at the United States Navy Yard, Washington, D. C., for the manufacture of cast iron shells until steel was substituted. The fact is that until a few years ago there was no-iron that could compete in any way with Muirkirk pig iron for strength and elasticity, and now there is none that would be preferred at the same price per ton. I have had charge of and practically owned this furnace for the past thirty-five years. I think I can truly say that I never have lost a customer except on account of price — never on account of quality.
CHAS. E. COFFIN."
Muirkirk, Prince George's County, Md. The need of cheap mixtures for medium and heavy castings, often calls for the use of coke and anthracite irons which carry a large percentage of iron or steel scrap. Mixtures are made of these irons that often come close to the strength given in Tables 52 to 55 for charcoal iron mixtures. Such castings as given in Nos. 23, 25 to 35, Chapter XXXV., page 252, are largely made of coke or anthracite iron mixed with scrap. As much as 80 per cent, of ordinary unburnt clean gray scrap iron can be mixed with 20 per cent. of 4 per cent, silicon pig iron for many lines of castings more than i ^ inches in thickness, and requiringowever, is the fact; and the credit of being able to make gun iron castings in the cupola that would stand the tests of the United States Government for gun carriage work rightfully belongs to Messrs. Robert Poole & Son Co. of Baltimore, Md., and Muirkirk pig iron made by me. This was in 1893. The War Department at first refused to accept cupola iron as gun iron, but when it was fully demonstrateduois Iron Co., Illinois Steel Co., Jefferson Iron Co., Kittan-ning Iron & Steel Co., C. A. Kelly Plow Co., Lebanon Furnace, Longdale Iron Co., Lackawanna Iron & Steel Co., Logan Iron........................ 16,720 " t-